考虑当地涡旋运动修正的湍流模型在非定常空化湍流流场计算中的应用

Applications of LSC turbulence model on unsteady cavitating flows

为了更精确地模拟当地涡旋运动对复杂非定常空化湍流流动的影响,考虑当地涡旋运动特性对标准k-ε湍流模型进行了修正;并采用该修正模型对二维Clark-Y水翼周围非定常空化湍流场进行了计算;通过与实验结果进行对比,分析并验证了该修正模型计算结果的有效性。研究表明:该修正湍流模型根据当地涡旋效应对湍动能输运方程中的生成项进行修正,可以有效解决标准k-ε模型对湍动能的过度预测问题,得到的空化核心区域时均湍动能和湍流黏性的预测结果降低了约30%,与实际值更为接近;标准k-ε模型计算所得的时均空泡长度不大于0.6倍弦长,而修正模型计算所得的时均空穴可以覆盖水翼吸力面;修正模型可以准确预测水翼吸力面表面空泡的非定常脱落过程,包括附着空穴的拉伸和断裂,以及脱落空泡的逐渐消失。

Local swirling correction(LSC) turbulence model is introduced for simulating the unsteady cavitating flows by considering local streamline curvature effect. The standard k-ε turbulence model is used to calculate the unsteady cavitating flows as a comparison. The LSC model can be validated by comparing with experimental cavity visualizations. Following conclusions can be drawn: the LSC model revises the turbulence production term.It can solve the problem that standard k-ε turbulence model over-predicts the eddy viscosity. It can get a 30% decreasing of turbulence kinetic energy and eddy viscosity in cavitating regions, according better with experimental results. Result using LSC turbulence model shows time average cavity that covers the whole suction surface, while that using standard k-ε turbulence model shows cavity with about 0.6-chord length. Local swirling effect can decrease time average turbulence eddy viscosity in cavity closure region effectively. LSC model can also capture time revolutions of cavitating flows better, including growth and breakup of attached cavity, as well as collapses of detached cavity.